Cassette and apparatus for liquid freezing

ABSTRACT

A cassette for use in freezing a liquid contained in a plurality of liquid receptacles comprises a bottom plate for supporting a number of the liquid receptacles in a layer, a number of intermediate plates having essentially the same dimensions as the bottom plate for placing on a layer of the liquid receptacles and supporting a further layer of liquid receptacles, and two opposite side walls being rigidly connected to the bottom plate for constituting a U-form therewith, so that each intermediate plate when placed on a layer of the liquid receptacles will be fixed laterally in relation to the side walls. A freezer for freezing of a liquid contained in a plurality of liquid receptacles comprises a freezing tunnel, the cassette, and a cassette holder having a stand, for supporting the cassette and a number of the intermediate plates separated form the cassette, the cassette holder being mobile for movement from a station for loading of the cassette with the liquid receptacles and the intermediate plates to the freezing tunnel for inserting the loaded cassette therein.

BACKGROUND OF THE INVENTION

The present invention generally relates to freezing a liquid,particularly blood plasma, in a liquid receptacle. More precisely, theinvention relates to a cassette and an apparatus for such a treatmentfor a relatively large liquid volume, i.e. using a relatively largenumber of liquid receptacles.

It is known from experience that blood plasma should be frozen as soonas possible after the drawing of the blood and the separation of theblood plasma. More precisely, at most two hours should elapse from thedrawing to the start of freezing. The freezing process itself shouldoccur quickly enough for the plasma to reach a temperature of about −30°C. within an hour. After freezing, the plasma is normally stored at atemperature of about −30° C. while awaiting transportation to, forexample, a processing facility.

Earlier known examples of liquid receptacles for plasma are plastic bagsor essentially parallelepipedal plastic receptacles, so called vials, inwhich the plasma is kept during handling from the drawing location tothe processing location.

It is also earlier known how to use different forms of cooling liquidbaths, cooling metal blocks having cavities corresponding to the liquidreceptacles and cooling air of high speed for freezing the known liquidreceptacles. Cooling with air jets is described in more detail in theinternational patent application WO97/30317.

Most of the known methods for freezing plasma are designed forrelatively small plasma quantities, i.e. for a relatively small numberof receptacles, and are not suited for enlargement to higher liquidvolumes and a consequential higher number of receptacles, as the manualhandling of the receptacles would be time-consuming. Reducing the numberof receptacles by increasing the volume of each receptacle is notpractically possible or even desirable when it comes to blood plasma asthe traceability is or may become a demand, which of course means that ablend of blood plasma from for instance different donors cannot beaccepted, or in some cases only to a limited extent.

However, EP 0732097 discloses the use of a cassette and a freezingtunnel. This cassette has a frame carrying three perforated and fixedplates above each other for supporting a plurality of plasma bags. Apressure plate and a spring device are provided above each fixed platein order to press the plasma bags against the fixed plate. Obviously,this approach is lacking in productivity as the loading and theunloading are circumstantial and the packing density of the plasma bagsis low.

SUMMARY OF THE INVENTION

The main object of the present invention is therefore to provide an easyand effective way of handling a relatively large number of liquidreceptacles from filling through freezing and to low temperaturestorage.

According to the invention, this object is obtained by means of acassette having the new features defined in claim 1. Preferredembodiments of the cassette are defined in claims 2-4.

These features enable: that in a first step a number of liquidreceptacles are placed in a layer on a bottom plate; that in a secondstep an intermediate plate is placed on the previous placed layer ofliquid receptacles; that in a third step a further number of the liquidreceptacles are placed in a layer on the previously placed intermediateplate; that the second and third steps are repeated a predeterminednumber of times; and that the plates and the liquid receptacles togetherare pushed into a freezing tunnel with a streaming cooling medium andare kept in the freezing tunnel until the liquid in all liquidreceptacles are frozen. Further, since the cassette has two oppositeside walls, which are rigidly connected to the bottom plate forconstituting a U-form, each intermediate plate when placed on a layer ofliquid receptacles will be fixed laterally in relation to the sidewalls.

It is obvious that the special plates used make it easy to arrange abatch with a great number of liquid receptacles separate from thefreezer tunnel itself and that this batch easily can be pushed Into thefreezer tunnel and after freezing as easy be taken out from the freezertunnel. This handling also means that the liquid receptacles at any timemay be identified very easily, for example by pointing a bar code readertowards bar codes being fixed on the liquid receptacles when filling theliquid. If the bar code reader is used to register the read data, aswell as the time and the identity of the individual using the bar codereader, in a suitable register, the whole treatment process will betraceable for each separate liquid receptacde.

Thus, the cassette has a bottom plate to support a number of liquidreceptacles in one layer, and a number of intermediate plates withsubstantially the same dimensions as the bottom plate to be placed oneach layer of the liquid receptacles and each supporting a further layerof liquid receptacles.

Preferably, each intermediate plate has means cooperating with the sidewalls so that each intermediate plate when placed on a layer of liquidreceptacles will be fixed lengthwise relative the side walls.

The liquid receptacles are preferably flexible and each intermediateplate has spacer means to fix the distance to the subjacent intermediateplate and the bottom plate, respectively.

Further the bottom plate and each intermediate plate have a number offull length ducts which extend in the plane thereof for admitting thecooling medium to flow through them and thereby cool the bottom plateand the intermediate plates when the cassette is in the freezing tunnel.

According to the invention a freezer is further provided having thefeatures that are stated in claim 5. Preferred embodiments of thefreezer are defined in claims 6-10.

The freezer has thus a cassette, which contains a bottom plate tosupport a number of liquid receptacles in a layer and a number ofintermediate plates having substantially the same dimensions as thebottom plate to be placed on each layer of liquid receptacles andsupporting a further layer of liquid receptacles; a cassette holder,which includes a frame to support the cassette and a number ofintermediate plates separated from the cassette; and a freezer tunnelfor a streaming cooling medium in which freezing tunnel a cassette withliquid receptacles is inserted from the cassette holder to be kepttherein until the liquid in all the liquid receptacles in the cassetteis frozen.

The cassette holder of the freezer preferably has a stand for placingthe intermediate plates leaning, in contact with each other andsuccessively displaced in height.

The cassette holder can further be mobile for movement from a stationfor loading the cassette with the liquid receptacles and theintermediate plates to the freezing tunnel for inserting the loadedcassette therein.

The cassette holder can preferably be made mobile by providing wheels onthe frame of the cassette holder.

As cooling medium, preferably air is used in the freezing tunnel, butalso other gaseous cooling media are possible.

BRIEF DESCRIPTIONS OF THE DRAWINGS

Preferred embodiments of the cassette and the freezer according to thepresent invention will be described in the following with reference tothe accompanying drawings, in which:

FIG. 1 is a schematic diagram and shows an embodiment of a freezingtunnel in a freezer according to the invention;

FIG. 2 is a perspective of a first embodiment of a cassette holder and acassette, which is a part of the freezer according to the invention;

FIG. 3 is a plan view of the cassette holder and the cassette in FIG. 2after being loaded with a number of liquid receptacles;

FIG. 4 is a cross section view along the line IV-IV in FIG. 3;

FIG. 5 shows in larger scale a partial cross section of one of theintermediate plates in the cassette in FIGS. 24;

FIG. 6 is a side view of a second embodiment of a cassette holderaccording to the present invention; and

FIG. 7 is a back view of the cassette holder of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an embodiment of a freezer includes a housing 1,which has a dosed circulation channel 2. In this channel 2 a fan 3 isprovided in series with a cooling battery 4 and a freezing tunnel 5. Acassette 6, shown in FIGS. 2-4, can be introduced into the freezingtunnel 5 via an opening in the housing 1, which can be closed by a lid7.

In operation, the fan 3 circulates the air in the circulation channel 2and thus through the cooling battery 4, where the air is cooled, and thefreezing tunnel 5, in which the air has a suitable temperature forfreezing.

The cooling battery 4 is via conduits 8 and 9 connected to aconventional cooling unit 10 and can for instance be an evaporator forits cooling medium. Alternatively, the cooling unit 10 may be integratedin the housing 1.

FIG. 2 shows the cassette 6 and a cassette holder 11 according to afirst embodiment. The cassette 6 itself has a U-form structure with abottom plate 12 and two opposite side walls 13 and 14 rigidly connectedto the bottom plate 12. A number of rectangular intermediate plates 15of about the same measures as the bottom plate 12 also belong to thecassette 6. Each intermediate plate 15 can then be put over the bottomplate 12 between the side walls 13, 14 and be fixed in its positionlaterally in relation thereto. Each intermediate plate 15 has twoopposite projections 16 (shown in FIG. 5) at two adjacent corners. Oneach intermediate plate 15, these projections 16 form means, which cancooperate with recesses 17 in the vertical edges of the side walls 13,14 for fixing the position of the intermediate plate 15 lengthwise inrelation to the side walls 13, 14.

The cassette holder 11 in FIG. 2 has a support 18 for the cassette 6 andtwo parallel and recessed guide walls 19, 20 at the same distance fromeach other as the side walls 13, 14 of the cassette. A cassette 6 isshown placed on the support 18 with the side walls 13, 14 as directextensions of the guide walls 19, 20. The intermediate plates 15 canthen be placed with their projections 16 inserted into their respectiverecesses 21 in the guide walls 19, 20 which thus together with a crossbar 22 form a stand for a somewhat sloping placement of the intermediateplates 15. In the position shown for cassette 6 in the cassette holder11 (FIGS. 2-4), the recesses 21 connect at one of their ends each to aseparate one of the recesses 17, and the other ends of the recesses 21are displaced in height, so that the intermediate plates 15, in thesloped placement in the stand, also are displaced in height and incontact with each other.

The support 18 and the recessed guide walls 19, 20 of the cassetteholder 11 form the upper part of a frame 23 of the same height as theopening in the freezing tunnel 5. The frame 23 is mobile on wheels 24,which means that the cassette 6 easily can be moved from the cassetteholder 11 into the freezing tunnel 5 of the freezer, and vice versa.

FIGS. 2-4 also illustrate how the loading of the cassette 6 withflexible liquid receptacles 25 is made.

In a first step, a number of liquid receptacles 25 are placed in a layeron the bottom plate 12.

In a second step, the intermediate plate 15 positioned next to thecassette 6 is lifted, guided by its projections 16 in the recesses 21,and is moved in between the side walls 13, 14 where it is placed on thepreviously placed layer of liquid receptacles 25, with its projections16 inserted each into a separate one of the recesses 17. The position ofeach intermediate plate 15 position transversely in relation to thebottom plate 12 is thus controlled by the side walls 13, 14. Further,the position of the intermediate plate 15 lengthwise over the bottomplate 12 is controlled by the engagement of the projections 16 with therecesses 17. Finally, the position of the intermediate plate 15 inheight over the bottom plate 12 is controlled partly by the engagementof the projections 16 with the recesses 17, and partly by spacer meansin form of two posts 26 at the opposite corners to the projections 16.Each intermediate plate 15 has further a handle 27, which is positionedbetween the posts 26.

In a third step, a number of liquid receptacles 25 are placed in a layeron the intermediate plate 15 placed on the liquid receptacles in thesecond step.

Thereafter, the second and third steps are repeated in a predeterminednumber of times, i.e. from zero to so many times as there are availableintermediate plates 15. Finally, an intermediate plate 15 can be placedon the top layer of the liquid receptacles 25.

As can be seen from FIG. 5, each intermediate plate 15 has a number offull length ducts, which extend in the plane of the intermediate plate15, to admit the cooling medium to flow through them and thereby coolthe intermediate plate 15, when the cassette 6 is in the freezing tunnel5. The projections 16 are provided each on a separate U-profile which isclosely connected to a longitudinal edge of the intermediate plate 15.

Preferably, the bottom plate 12 also has similar full length ducts. Theintermediate plate 15 is, as the bottom plate 12, preferably made of alight and good heat-transferring material, for instance aluminum or anyother light metal or light metal alloy.

As indicated in FIG. 2, the intermediate plate 15 can along its sideedge with the handle 27 have a number of openings 28, more precisely onesuch opening 28 for each liquid receptacle 25, which is intended to beplaced on the intermediate plate 15. The equivalent Is also valid forthe bottom plate 12. These openings 28 are designed for placingtest-tubes, which in some cases are annexed each to a separate liquidreceptacle 25. Each test-tube contains the same blood plasma as theliquid receptacle to which it is annexed and should be placed in avertical position during freezing. Since the height of the test-tubesmay be greater then the height of the posts 26 defining the spacingbetween the intermediate plates 15, the test-tubes may be placed inopenings alternating between the left and the right half side of theintermediate plates 15, as illustrated in FIG. 2

In order to obtain a good heat transfer between the intermediate plates15 and the liquid receptacles 25, the latter preferably are so flexibleas to make contact with the intermediate plates 15 over as large area aspossible.

It is obvious that the invention implies that a cassette 6 can be loadedwith liquid receptacles 25 in a simple and ergonomic way, separated fromthe freezing tunnel 5 itself, for example at a specially for thispurpose provided production station. Further, the fully loaded cassette6 can easily be moved on the cassette holder 11 to the freezing tunnel 5where it could be docked in order to easily be pushed into this and,after completed freezing of the liquid in the liquid receptacle 25, aseasily be taken out from the freezing tunnel 5 and be placed on thecassette holder 11, which later easily can be moved to a space, wherethe frozen liquid receptacles 25 are transferred to package for storingor to transport package for transfer to another place, which is providedfor further storage of the liquid receptacles. Here, the liquidreceptacles 25 with the frozen liquid are easily removed from thecassette 6 by raising the intermediate plates 15 one by one and thenpushing each one into its sloped position in the stand 22-24 of thecassette holder 11.

For the displacement of cassette 6 in relation to the cassette holder11, this later has a number of rolls 29, on which the cassette 6 isplaced. Further, there is a coupling mechanism (not shown) that can keepthe cassette 6 in a desired fixed position on the cassette holder 11 andalso release the cassette 6 so that it can be pushed on the rolls 29.

A second embodiment of a cassette holder 30 is illustrated in FIGS. 6and 7 as including a lifting equipment 31 for raising and lowering thecassette 6 on the cassette holder 30 such that the intermediate plates15 may be positioned at substantially the same height in their stand 32on the cassette holder 30.

The lifting equipment 31 illustrated comprises a tresor 33 positionedbetween an upper plate 34 for carrying the cassette 6 and a lower fixedsurface 35. An electric motor 36 is provided for driving an elevatingscrew 37 to raise or lower the upper plate 34 in accordance withinstructions received from a control box 38. During these movements thetresor 33 keeps the upper plate 34 horizontal and parallel to the lowerfixed surface 35.

The stand 32 has two guide walls 39, 40, a bottom plate 41 and a backplate 42. The two guide walls 39,40 correspond to the guide walls 19, 20illustrated in FIGS. 2-4 but have no recesses 21 for the projections 26of the intermediate plates 15, since such recesses are unnecessary asthe height position of the cassette 6 is adjusted by the liftingequipment. The bottom plate 41 may be horizontal or slightly slantingbackwards from the cassette 6. The back plate 42 may be substantiallyvertical or slightly sloping backwards.

When starting the loading of a cassette 6 the lifting equipment 31 holdsthe cassette 6 in an uppermost position. The lifting equipment 31 thenlowers the cassette 6 stepwise for each intermediate plate 15 that is tobe placed on the liquid receptacles 25 between the side walls 13, 14 ofthe cassette 6. When unloading the liquid receptacles 25 with frozenliquid from the cassette 6, the lifting equipment 31 first holds thecassette 6 in a lowermost position and then raises the cassette 6stepwise for each intermediate plate 15 that is raised from the cassette6 and placed in the stand 32.

Consequently, the loading and unloading operations are extremelyergonomic as the liquid receptacles 25 are being handled atsubstantially the same height all the time.

It will be understand that various changes and amendments of the abovedescribed embodiment may be made by those skilled in the art within thescope of the invention as expressed in the appended claims.

In one modification, the stand of the cassette holder 11 for placing ofthe intermediate plates 15 may be released from the frame 23 of thecassette holder, which means that the stand does not have to follow thecassette 6, when this is moved on the cassette holder 11 from aproduction station to the freezing tunnel 5. The stand could also bemore or less permanently fixed to the production station.

Finally, the invention is well suited for freezing other liquids,although it is primarily meant for freezing blood plasma.

1. A cassette for use in freezing a liquid contained in a plurality ofliquid receptacles (25), said freezing comprising inserting the cassette(6) with the liquid receptacles (25) into a freezing tunnel (5) having astreaming cooling medium and keeping them therein until the liquid inall the liquid receptacles (25) in the cassette (6) is frozen,comprising: a bottom plate (12) for supporting a number of the liquidreceptacles (25) in a layer, a number of intermediate plates (15) havingessentially the same dimensions as the bottom plate (12) for placing ona layer of liquid receptacles (25) and supporting a further layer ofliquid receptacles (25), and two opposite side walls (13, 14) beingrigidly connected to the bottom plate (12) for constituting a U-formtherewith, so that each intermediate plate (15) when placed on a layerof liquid receptacles (25) will be fixed laterally in relation to theside walls (13, 14).
 2. A cassette as claimed in claim 1, wherein eachintermediate plate (15) has means (16) cooperating with the side walls(13, 14) so that each intermediate plate (15) when placed on a layer ofliquid receptacles (25) will be fixed lengthwise in relation to the sidewalls (13, 14).
 3. A cassette as claimed in claim 2, wherein the liquidreceptacles (25) are flexible and each intermediate plate (15) hasspacer means (16, 26) determining the distance to the subjacentintermediate plate (15) and the bottom plate (15), respectively.
 4. Acassette as claimed in claim 1, wherein each intermediate plate (15) andthe bottom plate (12) have a number of full length ducts extending inthe plane of the plate for admitting the streaming of the cooling mediumthrough them and thereby a cooling of the bottom plate (12) and theintermediate plates (15), when the cassette (6) is inserted in thefreezing tunnel (5).
 5. A freezer for freezing a liquid contained in aplurality of liquid receptacles (25) said freezer comprising a cassette(6) for supporting the liquid receptacles (25) and a freezing tunnel (5)for a streaming cooling medium, the cassette (6) with the liquidreceptacles (25) being insertable into the freezing tunnel (5) and kepttherein until the liquid in all the liquid receptacles (25) in thecassette (6) is frozen, wherein the cassette (6) comprises a bottomplate (12) for supporting a number of liquid receptacles (25) in a layerand a number of intermediate plates (15) having substantially the samedimensions as the bottom plate (12) for being placed each on a separatelayer of liquid receptacles (25) and each supporting a further layer ofliquid receptacles (25), a cassette holder (11; 30) is provided having aframe (23) for supporting the cassette (6) and a number of intermediateplates (15) separated from the cassette (6), and the cassette holder(11; 30) is mobile for movement from a station for loading of thecassette (6) with the liquid receptacles (25) and the intermediateplates (15) to the freezing tunnel (5) for inserting the loaded cassette(6) therein.
 6. A freezer as claimed in claim 5, wherein the cassetteholder (11; 30) has a stand (20-22; 32) for placing the intermediateplates (15) in a sloping or substantially vertical position in contactwith each other and successively displaced in height.
 7. A freezer asclaimed in claim 6, wherein the frame (23) of the cassette holder (11)is equipped with wheels (24).
 8. A freezer as claimed in claim 5,further comprising lifting equipment (31) for raising and lowering thecassette (6) on the cassette holder (30) such that the intermediateplates (15) may be loaded and unloaded at substantially the same height.9. A freezer as claimed in claim 5, wherein the cooling medium of thefreezing tunnel (5) is air.
 10. A freezer as claimed in claim 6, whereinthe stand for placing the intermediate plates (15) is releasable fromthe frame of the cassette holder.
 11. A cassette as claimed in claim 2,wherein each intermediate plate (15) and the bottom plate (12) have anumber of full length ducts extending in the plane of the plate foradmitting the streaming of the cooling medium through them and thereby acooling of the bottom plate (12) and the intermediate plates (15), whenthe cassette (6) is inserted in the freezing tunnel (5).
 12. A cassetteas claimed in claim 3, wherein each intermediate plate (15) and thebottom plate (12) have a number of full length ducts extending in theplane of the plate for admitting the streaming of the cooling mediumthrough them and thereby a cooling of the bottom plate (12) and theintermediate plates (15), when the cassette (6) is inserted in thefreezing tunnel (5).